In diagnosing and treating certain medical conditions, it is often desirable to perform a biopsy, in which a specimen or sample of tissue is removed for pathological examination, tests and analysis. As is known, obtaining a tissue sample by biopsy and the subsequent examination are typically employed in the diagnosis of cancers and other malignant tumors, or to confirm that a suspected lesion or tumor is not malignant. The information obtained from these diagnostic tests and/or examinations is frequently used to devise a plan for the appropriate surgical procedure or other course of treatment. For example, breast biopsies may be taken where a suspicious lump or swelling is noticed in a breast. Examination of tissue samples taken by biopsy is of particular significance in the diagnosis and treatment of breast cancer. In the ensuing discussion, the biopsy and treatment site described will generally be the human breast, although the invention is suitable for marking biopsy sites in other parts of the human and other mammalian body as well.
After the biopsy sample is taken, it may take several days or weeks before the results of the examination of the sample are obtained, and still longer before an appropriate treatment decision is reached. If the decision involves surgery it is clearly important for the surgeon to find the location in the breast from where the tumor tissue has been taken in the biopsy procedure, so that the entire tumor and possibly surrounding healthy tissue can be removed.
However, radiographically visible tissue features, originally observed in a mammogram, may be removed, altered or obscured by the biopsy procedure. In order for the surgeon or radiation oncologist to direct surgical or radiation treatment to the precise location of the breast lesion several days or weeks after the biopsy procedure was performed, it is desirable that a biopsy site marker be placed in or on the patient's body to serve as a landmark for subsequent location of the lesion.
Various types of biopsy site markers have been described, including visible markers applied externally to the patient's skin, radiographically (X-ray)-detectable tissue markers such as clips and staples, and ultrasound-detectable markers, have also been described. X-ray-detectable marker wires may be inserted through a biopsy needle, leading from the surface of the patient's body to the biopsy site. Some markers may be biodegradable.
However, due to the consistency of breast tissue and the fact that these biopsy site markers are typically introduced while the breast is still compressed between the mammography plates, prior art biopsy markers may not remain at the specific biopsy location after the breast has been decompressed and removed from the mammography apparatus, and may suffer from additional disadvantages as well. In order to locate an X-ray-detectable marker left at a biopsy site, an additional mammography is generally required at the time of follow up treatment or surgery. In addition, once it is located using mammography, the biopsy site must usually be marked again with a location wire that is visible by eye to provide guidance to the clinician performing the treatment or surgery. However, as the patient is removed from the mammography apparatus, or otherwise transported, the position of the location wire can change or shift before the treatment or surgery is performed, which may result in treatments being misdirected to undesired locations. Furthermore, at least some prior art biopsy site markers can remain present at the site of implantation for an indefinite period of time and, if not surgically removed, may obscure or otherwise interfere with any subsequent mammography or imaging studies.
However, due to the large amount of fibrous tissue normally present in a human breast, and due to the presence of ligaments running through the breast, a marker that simply has a bright signal alone will not provide a useful signal that is readily discernable from the many anatomic features normally present within a human breast. Such markers are typically small, being sized to fit within a syringe or other delivery tube, and so are often not readily distinguishable from natural features of the breast, which include occasional small ultrasound-bright spots.
As an alternative or adjunct to radiographic imaging, ultrasonic imaging and visualization techniques (abbreviated as “USI”) can be used to image the tissue of interest at the site of interest during a surgical or biopsy procedure or follow-up procedure. USI is capable of providing precise location and imaging of suspicious tissue, surrounding tissue and biopsy instruments within the patient's body during a procedure. Such imaging facilitates accurate and controllable removal or sampling of the suspicious tissue so as to minimize trauma to surrounding healthy tissue.
For example, during a breast biopsy procedure, the biopsy device is often imaged with USI while the device is being inserted into the patient's breast and activated to remove a sample of suspicious breast tissue. As USI is often used to image tissue during follow-up treatment, it may be desirable to have a marker, similar to the radiographic markers discussed above, which can be placed in a patient's body at the site of a surgical procedure and which are visible using USI. However, radiopaque markers may not be visible with USI. A marker visible with USI enables a follow-up procedure to be performed without the need for traditional radiographic mammography imaging which, as discussed above, can be subject to inaccuracies as a result of shifting of the location wire as well as being tedious and uncomfortable for the patient.
Thus, there is need in the art for biopsy site markers that are deliverable into the cavity created by removal of the biopsy specimen and not into tissue that is located outside of that biopsy cavity, and which will not migrate from the biopsy cavity even when the breast tissue is moved, manipulated or decompressed. Moreover, such desired markers should remain detectable at the biopsy site (i.e., within the biopsy cavity for a desired time period); should not interfere with imaging of the biopsy site and adjacent tissues at a later time; and should be readily distinguishable in the various imaging procedures from lines of calcifications which frequently are signs for a developing malignancy.